1. Field of the Invention
The present invention relates to a power use circuit breaker and an electrical circuit arrangement for an electrical power generating plant using such power use circuit breaker.
2. Conventional Art
A power use circuit breaker, which interrupts a fault current flowing at a time of electric power system accident and protects the electric power system, is required to instantly interrupt a large fault current. In particular, a power use circuit breaker disposed between an electric power generator and a main power transformer, which is opened and closed at the time of starting and stopping of the electric power generator and further interrupts a large power generator fault current flowing at the time of accident, is required to have a capacity of interrupting a large current from several ten thousand to several hundred thousand amperes (A) containing a DC component.
A power use circuit breaker such as a puffer type gas circuit breaker and a vacuum circuit breaker which have been used to interrupt such large current has the following drawbacks.
(a) Puffer Type Gas Circuit Breaker
It is required a gas pressure of more than several hundred thousand atmospheric pressure which is to be blasted to a large current arc generated between contacts during current interruption to extinguish the arc for interrupting current of several ten thousand amperes, therefore, if a bellows having an operating stroke of 100xcx9c300 mm in order to obtain the above high pressure gas, an operating force of about hundred thousand-several tens of tons is required which increases the size of the machine.
(b) Vacuum Circuit Breaker
When interrupting a current containing a DC current component with a vacuum circuit breaker, it is impossible to attenuate the DC current component by making use of an arc resistance, because an arc voltage generated between contacts in the vacuum circuit breaker during current interruption is low, therefore, it is difficult to apply a vacuum circuit breaker for interrupting current in an electric power generator main circuit containing a large DC current component. Further, since a current conducting capacity of a vacuum circuit breaker is small, it is difficult to use a vacuum circuit breaker in a circuit in which current more than 4000 A flows.
An object of the present invention is to provide a small sized power use circuit breaker which realizes current conduction and interruption of a large current containing a DC current component.
Another object of the present invention is to provide a small sized power use circuit breaker which surely performs current interruption of a large current containing a DC current component with a small operating force.
Still another object of the present invention is to provide an electric circuit arrangement for an electric power generating plant which permits a size reduction of the concerned house installation by making use of a small sized power use circuit breaker.
A power use circuit breaker according to the present invention which is connected in an electric circuit and operates to interrupt current flowing through the electric circuit, is characterized by being provided with an electrical resistance generating unit which adds an electrical resistance in the electric circuit during interruption of current and causes to attenuate current to be interrupted and a vacuum circuit breaker which is connected in electrically series with the electrical resistance generating unit and operates to interrupt the attenuated current.
Further, a power use circuit breaker according to the present invention including a current interrupting circuit which is connected in an electric circuit and operates to interrupt current flowing through the electric circuit and a current conducting circuit which is connected in parallel with the current interrupting circuit and is opened prior to the current interrupting circuit during interruption of current so as to transfer conducting current to the current interrupting circuit, is characterized in that the current interrupting circuit is provided with an electrical resistance generating unit which adds an electrical resistance in the electric circuit during interruption of current and causes to attenuate current to be interrupted and a vacuum circuit breaker which is connected in electrically series with the electrical resistance generating unit and operates to interrupt the attenuated current.
Further, it is characterized that the electrical resistance generating unit is an arc generating switching unit which is closed during current conduction to show a substantially negligible small value of electrical resistance and is opened during current interruption so as to generate an arc and to form an arc resistance circuit.
Further, it is characterized that the electrical resistance generating unit is provided with a container which contains gas of which pressure is raised by heating through arcing and the pressurized gas is blasted toward the arc.
Further, it is characterized that the current conducting circuit is provided with a current conducting switching unit, and the vacuum circuit breaker and the current conducting switching unit are coupled through an operating mechanism having a dead band with regard to operation stroke so as to open the vacuum circuit breaker after having opened the current conducting switching unit which permits an interlocked switching operation of the current conducting switching unit and the vacuum circuit breaker with a single driving unit.
Further, it is characterized in that the current conducting circuit is provided with a current conducting switching unit, and the vacuum circuit breaker, the arc generating switching unit and the current conducting switching unit are coupled through an operating mechanism having a dead band with regard to operation stroke so as to open the arc generating switching unit to generate an arc after having opened the current conducting switching unit and thereafter to open the vacuum circuit breaker which permits an interlocked switching operation of the current conducting switching unit, the arc generating switching unit and the vacuum circuit breaker with a single driving unit.
Further, it is characterized in that the current conducting switching unit and the arc generating switching unit are interlocked like a unitary body.
An electric circuit arrangement for an electric power generating plant according to the present invention, is characterized in that a power use circuit breaker according to one of those explained above is connected between an electric power generator and a main power transformer so as to permit separation of the main power transformer and a house transformer from the electric power generator.